Assessing the efficacy of antidepressants: the transactional paradigm.

Extant pharmacological literature seems to indicate that antidepressants are the most effective treatment for depression. However, there are flaws in the traditional paradigm for evaluating the efficacy of antidepressants. The traditional paradigm in pharmacology has adopted a biologically monistic causal structure, suggesting that the efficacy of antidepressants resides exclusively in biological pathways. The current paradigm in pharmacology has ignored the potential impact of psychological factors associated with the efficacy of antidepressants. This has occurred because psychological effects are seen as being a "paradigmatic anomaly," phenomena that are at odds with the traditional paradigm. Thus, the psychological factors associated with the administration of antidepressants have collectively been labeled as a "placebo effect" and discounted as a potential treatment pathway. However, empirical evidence suggests that the psychological factors, such as the formation of patient expectancies and a therapeutic alliance between physician and patient, increase the efficacy of antidepressants. Consequently, the current paper proposes the adoption of a transactional model that reflects the reciprocal interaction between psychological and biological factors associated with the efficacy of antidepressants.